It is known in the art to provide air cooled grates for progressive cooling of hot cement clinker discharge from the end of a cement kiln. The most relevant prior art for the purpose is disclosed in U.S. Pat. No. 4,460,333 filed on Aug. 26, 1982. Such patent discloses a modular cooler grate unit comprising a cast metal plate provided with a depending pusher flange extending across the front end thereof. The plate is provided with a plurality of air hole openings extending vertically and horizontally therethrough. On the bottom side of the plate, a plurality of ribs or fins extend lengthwise thereof between the successive rows of holes. The fins are of zigzag configuration so that they undulate between the successive holes in the adjacent rows. Such grates are employed in a cooling bed which consists of a plurality of side by side columns of overlapping rows of perforated grates through which air is directed upwardly. The hot clinker discharged from a cement kiln is advanced along the bed of grates by horizontally reciprocating alternate rows of grates relative to adjacent stationary rows of grates. The cooler grates are subject to high temperature, high corrosion and abrasion during the process of cooling the clinker.